Ladle

ABSTRACT

Inert gas supply nozzle is mounted on a ladle body in such a manner its output-side end surface is inclined upward, relative to the bottom surface of a molten material passageway portion, in a direction toward a molten material discharge opening formed in the ladle body. Even when a portion of the molten material flows upward toward the nozzle&#39;s output-side end, that portion can be reliably prevented from entering the output-side end portion of the nozzle, by virtue of the inclined end surface. Thus, the inert gas supply nozzle can function to supply the inert gas into the molten material in a stable manner over a long period of time.

FIELD OF THE INVENTION

The present invention relates generally to ladles for supplying (or resupplying) molten metal (hereinafter referred to as “molten material”), such as molten aluminum, from melting furnaces to molten material holding furnaces. More particularly, the present invention relates to an improved ladle which allows inert gas to be emitted from a nozzle into molten material with enhanced efficiency.

BACKGROUND OF THE INVENTION

Heretofore, during transfer of molten material from a melting surface to a molten material holding furnace, the molten material would produce hydrogen gas by drawing in vapor present in the air, and the thus produced hydrogen gas would then produce undesired cavities in workpieces cast by a casting process, therefore often resulting in unsatisfactory product quality.

In order to avoid the inconvenience, it has been generally conventional to perform a degassing process within the molten material holding furnace. Japanese Patent No. 3194418, for example, discloses a technique of performing not only such a degassing process within the molten material holding furnace, but also a degassing process prior to the molten material transfer to the holding furnace.

FIG. 6 shows a funnel disclosed in the above-mentioned No. 3194418 Japanese patent, and the disclosed funnel 1 includes a molten material reservoir 4 having a bottom surface 4 a, a molten material delivery section 5, an outlet or discharge opening 6 and an inert gas supply section 7. The disclosed funnel 1 is a type of auxiliary device used to transfer molten material from a ladle into a molten material holding furnace, and, in the funnel 1, the inert gas supply section 7 is disposed in the neighborhood of a boundary between the reservoir 4 and the delivery section 5. The supply section 7 comprises a porous plug positioned in proximity to the bottom surface 4 a of the molten material reservoir 4.

However, with the technique of the Japanese patent, a great amount of air would be unavoidably drawn in as the molten material is relocated from the ladle to the funnel 1 that is interposed between the ladle and the molten material holding furnace. Further, because the inert gas supply section 7 is positioned near the discharge opening 6, the supply section 7 would be undesirably clogged with the molten material unless the molten material is sufficiently drained off the supply section 7 after completion of the discharge, from the funnel, of a given amount of the molten material. For avoiding the clogging problem, there might be employed an approach of causing the supply section 7 to always emit inert gas; however, in this case, the production costs would increase considerably due to wasteful use of the inert gas.

SUMMARY OF THE INVENTION

In view of the foregoing prior art problems, it is an object of the present invention to provide an improved ladle which can contribute to improvement in the quality of cast products, by reliably preventing clogging of an inert gas supply section to thereby enhance an inert gas supply efficiency so as to prevent introduction, into a molten material holding furnace, of unwanted hydrogen gas.

In order to accomplish the above-mentioned object, the present invention provides a ladle for transferring molten material from a melting furnace (e.g., aluminum melting furnace) to a molten material holding furnace attached to a casting machine, which comprises: a ladle body having a molten material discharge opening and a molten material passageway portion leading to the molten material discharge opening; and an inert gas supply nozzle mounted on the ladle body adjacent the molten material discharge opening for emitting inert gas into the molten material. In the ladle of the present invention, the inert gas supply nozzle has a distal or output-side end surface located in the molten material passageway portion and inclined upward, relative to the bottom surface of the molten material passageway portion, in a direction toward the molten material discharge opening.

The ladle is a device for taking a necessary amount of the molten material from the melting furnace and transferring the taken molten material to the molten material holding furnace. When the molten material is poured from the ladle into the molten material holding furnace, the inert gas supply nozzle mounted on the ladle body emits the inert gas into the molten material, so as to appropriately deal with unwanted hydrogen gas produced from vapor in the air.

As the most important feature of the present invention, the inert gas supply nozzle of the ladle has its output-side end surface located in the molten material passageway portion and inclined upward, relative to the bottom surface of the molten material passageway portion, in a direction toward the molten material discharge opening. Thus, the output-side end surface of the nozzle is oriented toward the molten material discharge opening, the molten material flowing along the molten material passageway portion can be prevented from directly impinging on the nozzle's output-side end surface. As a result, the present invention can effectively eliminate the possibility of the output-side end portion of the nozzle being clogged with the molten material.

Further, with the output-side end surface of the nozzle, oriented toward the molten material discharge opening, the inert gas emitted from the nozzle can function to push the molten material along the passageway portion to the molten material discharge opening. Thus, at the last phase of the molten material pouring from the ladle into the holding furnace, in particular, the emitted inert gas can effectively push the molten material, remaining at and around the discharge opening, into the holding furnace, so that the molten material can be drained off the nozzle with significantly enhanced efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS

Certain preferred embodiments of the present invention will hereinafter be described in detail, by way of example only, with reference to the accompanying drawings, in which:

FIG. 1 is a view illustrating an example manner in which is used a ladle constructed in accordance with an embodiment of the present invention;

FIG. 2 is a sectional view of the ladle of the present invention;

FIG. 3 is a front view of the ladle of the present invention;

FIGS. 4A and 4B are views explanatory of behavioral differences between a conventional inert gas supply nozzle and an inert gas supply nozzle employed in the ladle of the present invention;

FIGS. 5A and 5B are views showing modified examples of the inert gas supply nozzle employed in the ladle of the present invention; and

FIG. 6 is a sectional view showing a conventional technique relevant to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Example manner in which a ladle of the present invention is used will be explained first, prior to a detailed description about structural features of the ladle.

FIG. 1 is a view illustrating the example use of the ladle of the present invention. Generally, the ladle 30 is required because a casting machine 20 is installed a certain appropriate distance from an aluminum melting furnace 10. Namely, the ladle 30 is initially positioned to front a tapping hole 11 of the aluminum melting furnace 10 in proximity thereto, so as to receive molten material (in this case, molten aluminum) from the tapping hole 11. The ladle 30 is movable as depicted by arrow {circle over (1)} and arrow {circle over (2)}, through operation of a robot arm 25, so as to front a molten material holding furnace 40 in proximity thereto; the holding furnace 40 is attached to the casting machine 20.

When molten material is to be poured from the ladle 30 into the molten material holding furnace 40, a lid 41 of the holding furnace 40 is opened and the ladle 30 is tilted to a suitable pouring position by means of the robot arm 25.

Pressurized inert gas is blown into the molten material holding furnace 40 via a pressurizing hole 42, so as to lower the bath level of the molten material in the holding furnace 40. Through such operation, the molten material held in the holding furnace 40 is supplied to a mold 44 via a stalk 43. As predetermined casting operations are repeated, the molten material in the holding furnace 40 decreases, so that there arises a need to resupply, as appropriate, the molten material from the melting furnace 10 to the holding furnace 40 using the ladle 30.

FIG. 2 is a sectional view of the ladle 30 of the present invention. The ladle 30 generally comprises a ladle body 31, a molten material discharge opening 32 formed in the ladle body 31, an inert gas supply nozzle 33 disposed adjacent the discharge opening 32, and a refractory lining (not shown).

The inert gas supply nozzle 33 has a distal or output-side end surface 36 located in a molten material passageway portion 34 leading to the discharge opening 32 and inclined upward, relative to a bottom surface 35 of the passageway portion 34 in a direction toward the discharge opening 32. Specifically, an angle θ between the nozzle's output-side end surface 36 and the bottom surface 35 of the passageway portion 34 is set to 10° or over, preferably to a range of 30° to 60°.

If the angle θ between the nozzle end surface 36 and the bottom surface 35 is below 10°, then the molten material would easily enter the output-side (i.e., lower) end portion of the nozzle 33. Thus, with a mounting error and tilting movement of the ladle 30 taken into account and to assure proper operation of the nozzle 33, it is desirable that the angle θ be 30° or over. However, if the angle θ exceeds 600, the flow of the inert gas ejected or emitted from the supply nozzle 33 would approximate the flow of the molten material, so that the emitted gas can not appropriately mix with the molten material. Therefore, the angle θ between the nozzle end surface 36 and the bottom surface 35 is preferably set to the range of 30° to 60°.

FIG. 3 is a front view of the ladle 30 of the present invention. The ladle body 31 is connected to a lower robot arm section 22 via a connection shaft 21 supported by bearings 26 and 27, and the connection shaft 21 can be rotated by a motor 28 so that the ladle 30 is allowed to vertically pivot or tilt via the connection shaft 21.

Next, a description will be given about behavior of the ladle 30 constructed in the above-described manner.

FIG. 4 is explanatory of the inert gas supply nozzle 33 employed in the ladle 30 of the present invention; more specifically, FIG. 4A is a view showing an example of a conventional inert gas supply nozzle employed in conventional ladles (hereinafter called “comparative example”), while FIG. 4B is a view showing the inert gas supply nozzle 33 employed in the ladle 30 of the present invention (hereinafter called “inventive example”).

In the comparative example of FIG. 4A, the inert gas supply nozzle 101 is mounted vertically at right angles to the bottom surface 103 of the molten material passageway portion 102. In this case, although the molten material generally flows in a direction of arrow {circle over (3)}, a portion of the molten material enters an output-side end portion of the nozzle 101 as depicted by arrow {circle over (4)} and may sometimes clog the end portion of the nozzle 101.

In the inventive example of FIG. 4B, the inert gas supply nozzle 33 is mounted obliquely in such a manner that the output-side end surface 36 is inclined upward, relative to the bottom surface 35 of the molten material passageway portion 34, in a direction toward the discharge opening 32 and thus oriented toward the discharge opening 32. The molten material flows in a direction of arrow {circle over (5)}, and, even when a portion of the molten material flows upward as depicted by arrow {circle over (6)}, that portion can be reliably prevented from entering the output-side end portion of the nozzle 36, by virtue of the inclined end surface 36. As a consequence, the inert gas supply nozzle 33 can function to supply the inert gas into the molten material in a stable manner over a long period of time.

FIG. 5A shows a modified example of the inert gas supply nozzle 33, which is mounted vertically downward toward and at right angles to the bottom surface 35 of the molten material passageway portion 34. The nozzle 33 has its output-side end surface 36 obliquely cut so as to be oriented toward the discharge opening 32. Thus, in this example too, the end surface 36 is inclined upward, relative to the bottom surface 35, in a direction toward the discharge opening 32.

In the illustrated example of FIG. 2 described above, the inert gas supply nozzle 33 has to be mounted obliquely on the ladle body 31; therefore, excessive care is required in positioning and fixing the nozzle 33 in an appropriate tilted posture. The inert gas supply nozzle 33 of FIG. 5A can be mounted to the ladle body 31 with increased ease as compared to the example of FIG. 2, because it only has to be positioned at right angles to the bottom surface 35. As a consequence, the necessary manufacturing costs of the ladle 30 can be lowered effectively.

FIG. 5B shows still another modified example of the inert gas supply nozzle 33, which has a curved output-side end portion with its end surface 36 inclined upward, relative to the bottom surface 35 of the molten material passageway portion 34, in a direction toward the discharge opening 32 and thus oriented toward the discharge opening 32. In this case, there is no need to obliquely cut the output-side (i.e., lower) end of the inert gas supply nozzle 33 and it suffices to merely curve the output-side end portion of the nozzle 33, unlike the inert gas supply nozzle 33 of FIG. 5A. Further, the inert gas supply nozzle 33 of FIG. 5B can be mounted to the ladle body 31 with increased ease as compared to the example of FIG. 2, because it only has to be mounted at right angles to the bottom surface 35. As a consequence, the necessary manufacturing costs of the ladle 30 can-be lowered effectively.

Because each of the examples of the inert gas supply nozzles 33, shown in FIGS. 4B, 5A and 5B, is constructed in such a manner that its distal or output-side end surface is inclined upward in a direction toward the molten material discharge opening 32, the molten material can be reliably prevented from entering the output-side end portion of the nozzle 33. Thus, the inert gas supply nozzle 33 can function to supply the inert gas into the molten material in a stable manner over a long period of time.

Further, with the output-side end surface of the nozzle 33, oriented toward the molten material discharge opening 32, the inert gas emitted from the nozzle 33 can function to push the molten material along the passageway portion 34 to the discharge opening 32. Thus, at the last phase of the molten material pouring from the ladle 30 into the holding furnace 40, in particular, the emitted inert gas can effectively push the molten material, remaining at and around the discharge opening 32, into the holding furnace 40, so that the molten material can be drained off with significantly enhanced efficiency.

In the above-described manner, the ladle 30 of the present invention allows the inert gas to be ejected from the nozzle 33 with enhanced efficiency and can thereby sufficiently degas the molten material. As a result, the ladle 30 of the present invention can minimize the unwanted cavities in cast products and thus permits product quality improvement.

Test was conducted on the lade 30 of the present invention in the following manner.

Casting Conditions:

-   -   Type of the inert gas supply nozzle used: type of FIG. 2;     -   Length of the inert gas supply time: 10 seconds;     -   Inert gas supply timing: from a start to end of the tilting         movement of the ladle;     -   Amount of the inert gas supplied: 800 cm³;     -   Amount of the molten material within the ladle: 22 kg; and     -   Type of the molten material used: aluminum alloy (JIS AC4C).

Evaluation:

-   -   Each cast product produced under the above-mentioned conditions         showed a dramatic reduction in the number of the unwanted         cavities.

Note that the distal or output-side end surface of the inert gas supply nozzle 33 may be shaped in any desired shape as long as it is inclined upward, relative to the bottom surface 35 of the molten material passageway portion 34, in a direction toward the molten material discharge opening 32. Further, whereas the ladle 30 of the present invention has been described as employing just one inert gas supply nozzle 33, any other desired number of the nozzles 33 may be employed.

Further, it should be appreciated that, whereas the ladle 30 of the present invention has been described above as handling molten aluminum alloy, the ladle 30 may be applied to cases where any other desired molten material, such as molten magnesium alloy, copper alloy, casting iron, etc., are handled.

In summary, the present invention is characterized in that the inert gas supply nozzle mounted on the ladle body has its distal or output-side end surface located in the molten material passageway portion and inclined upward, relative to the bottom surface of the molten material passageway portion, in a direction toward the molten material discharge opening. With such arrangements, the ladle of the present invention can contribute to improvement in the quality of cast products by reliably preventing clogging of the inert gas supply nozzle to thereby enhance the inert gas emission efficiency.

Obviously, various minor changes and modifications of the present invention are possible in the light of the above teaching. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described. 

1. A ladle for transferring molten material from a melting furnace to a molten material holding furnace attached to a casting machine, said ladle comprising: a ladle body having a molten material discharge opening and a molten material passageway portion leading to said molten material discharge opening; and an inert gas supply nozzle mounted on said ladle body adjacent said molten material discharge opening for emitting inert gas into the molten material, wherein said inert gas supply nozzle has an output-side end surface inclined upward, relative to a bottom surface of said molten material passageway portion, in a direction toward said molten material discharge opening. 